Rubber coated steel object and method of making the same



May 21, 1935. E. c. DOMM 2,002,251

RUBBER COATED STEEL OBJECT AND METHOD OF MAKING THE SAME Filed April 10, 1953 Copper fufier fiverzz or' Patented May. 21, 1935 UNITED STATES PATENT OFFICE RUBBER COATED STEEL OBJECT METHOD OF MAKING THE SAME Elgin Carlton Domm, Niles, Mich., assignor to National Standard- Company, a corporation of Michigan Application April 10, 1933, Serial No. 665,425

18 Claims.

It has heretofore been known that steel wires, I

5 coated with brass, could be vulcanized directly to clean.

rubber. In'connection with the flexible articles of small cross-sectional area, it has proved impractical to hot dip the articles in molten brass because of the effect upon the physical characteristics of the articlefor example, a wire. Moreover, it has proved difficult to ele'ctroplate a brass coating. It was also believed heretofore that pure copper would not bond satisfactorily with rubber.

It has now been discovered that if a steel article, for example, a steel tire bead reenforcing wire, or a flexible steel strip, is coated with a zinc coating, either electrolytically or by dipping in molten zinc, and is then electroplated with pure copper, it may be very satisfactorily bonded to rubber. It is believed that the reason for this adhesiveness to rubber is due to the fact that the zinc and copper form an alloy after deposition upon the wire. This alloy is indicated by a change in the color of the copper, which, under ordinary circumstances, will fade to a brass colored appearance in a month or so, when in a layer of one one hundred thousandths of an inch in thickness. It is likewise probable that any alloying is very materially accelerated by the temperature of the vulcanization operation.

The rubber coated wire or strip produced in this manner has good or better physical characteristicsthan the original object. The temperature of the zinc bath is not high enough to destroy the flexibility of the article, but on the contrary, if properly controlled, may be used to materially increase the elongation limit and elasticity .of the article.

The invention is illustrated diagrammatically in the drawing, wherein Figure 1 shows a broken view of a wire cut away to show the various coatings, and Fig. 2 isan end View of the same. It is to be understood that the distinct layers of zinc and copper are shown for the purpose of illustration only. The drawing is necessarily very much out of scale.

In carrying out the process, great care must be exercised at all times to have the steel article Likewise the electro-platlng of copper upon the zinc must be carefully controlled in order to avoid difilculties such as blistering.

' wire.

inch. These wires have a typical composition as follows:

Percent Carbon .65 Manganese .80 5 Phosphorous- .015 Sulphur .025 Silicon .095

Balance is iron with traces of impurities.

The wires may be fed continuously from swifts, or the like, through the entire system. They are first cleansed by scraping and then wiping with rags soaked in a grease solvent, such as gasoline. They are then further cleansed by passing through a bath of hydrochloric acid, preferably containing about I-ICl. The excess acid is removed by wet rags, and the wires then passed through a water bath. They are again passed through acid, this time about 8% H01 and are again wiped and washed. The number and extent of these cleansingtreatments depends, of course, upon the original condition of the wire.

The wires, when thoroughly clean, are drawn through a fiux, such as a saturated solution of zinc ammonium chloride, the excess solution is removed by a rag wipe, and the wires then drawn through a bath of molten zinc.

The temperature of the zinc bath is particularly important in connection with the tire bead reenforcing wires. The bath must not be so'hot as to injure the physical characteristics of the It has been found that by proper adjustment of the temperature of the bath the wire may actually be improved. For example, it is desirable that tire bead wires should have a rather high limit of elongation and elasticity. As produced, such wire ordinarily has an elongation limit of to 1 By maintaining the zinc bath at proper temperatures, this may be considerably increased. For example, with wires of .037 to .043 inch in diameter, an immersion of 1 to 5 seconds in a zinc bath held, at 820 to 840 degrees F. may cause an increase in elongation limit from to 1 /q% in the orlginalwire to 2% to 5% after treatment. At the same time the elastic limit of the wire may be increased from 65 to 85%. For example, the wire may be passed through a 3 to foot bath of zinc at 180 feet per minute, the zinc being maintained at 840 degrees F.

The steel article acquires a coating approximately 1/4000 to 1/11000 of an inch in thickness. For example, with wire of .043 inch diameter, weighing 4.88 lbs.rper 1000 feet of wire, the weight of the zinc is about 8 to 20 grams per kilogram of wire. With .037 inch diameter wire, weighing 3.61 lbs. per 1000 feet, the weight of the zinc is about 10 to 24 grams per kilogram.

The zinc alloys itself with the iron to some extent, so that about 10 to of the zinc coating is iron. This results in a better bonding than where the zinc is applied electrolytically;

After leaving the zinc bath, the excess zincis removed by an asbestos wiper, and the wire is then drawn while still quite warm (within one or two seconds after leaving the zinc bath) through a bath of dilute caustic soda, containing about 5% sodium hydroxide. The caustic generates a quantity of hydrogen by action upon the zinc, and itis believed that this action has a favorable effect upon the copper plating, possibly because of adsorption of the nascent hydrogen.

The wires are then washed in warm water and passed into a copper plating bath. The plating is preferably carried out by the cyanide process using a solution containing 4 oz. of sodium cyanide, 3 oz. of copper cyanide, 2 oz. of sodium carbonate and A; oz. sodium hyposulphite per gallon. Generally several consecutive plating baths are used. At each end of the plating tanks the wire is fed over copper rolls to which a low voltage direct plating current is supplied in sufilcient amperage and voltage to plate the wire. A normal current density is amperes per square foot.

' The electrolyte is continuously circulated, and

- a portion thereof is continuously removed from the tank, warmed to about 120 F. and replaced. This flow of electrolyte is particularly advantageous in removing gas bubbles.

Copper is applied at the rate of 0.5 to 1.3 grams per kilogram of wire. The proportion-of zinc to copper is therefore from 6 to 30 parts of zinc to one part of copper.

The weight of0.5 gram of copper per kilogram of .043 inch diameter tire bead wire is equivalent to a thickness of approximately 1/240,000 inch of the metal on the average. Thisv amount is also equivalent to a weight of approximately 0.1 gram of copper per square foot of surface. A normal thickness of the zinc is about 1/6000 of an inch, and it is preferred that the copper be approximately 1/10 to 1/20 of this thickness, or from 1/60,000 to l/120,000 of an inch.

After leaving the plating bath the wires are washed with water, first cold and then hot, and are then air dried.

After the steel articles have been zinc and copper plated, they may be coated with rubber and the rubber vulcanized directly thereto in ac-- cordance with known practice.

Other rubber adhesion increasing coating such as antimony may, of course, be added if desired. Likewise, other substances may be added to the zinc to accomplish particular qualities in the finished product.

- The coating of zinc lessens or prevents corrosion of the material to which it is applied; and the copper alone; or alloying with the zinc, increases the bonding or adhesion to rubber when the article is employed in rubber.

The foregoing detailed description has been given for clearness of understanding only, and

no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible-in view of the prior art. v 4

What I regard as new, and desire to secure by Letters Patent, is:

1. In the production of brass coated ferrous base articles," the step of producing a brass coating by separately coating said article with a thin layer of zinc, and a layer of copper having a thickness less than approximately 1/60,000 inch, and of a thickness to alloy throughout with the zinc at atmospheric temperature or at the temperature of vulcanization and produce a thin layer of brass thereon, and vulcanizing a coating of rubber thereon.

2. The method asset forth in claim 1 in which the zinc layer has a thickness of the orderof 1/4000 to 1/11,000 of an inch.

3. The method as set forth in claim 1 in which the copper has a thickness of the order of l/240,000 inch to 1/60,000 inch.

4. The method as set forth in claim 1 in which the zinc layer has a thickness of the order of 174,000 to 1/11,000 inch, and the copper has a thickness of the order of 1/60,000 to 1/240.000 inch.

5. The method as set forth in claim 1 in which the zinc is alloyed with the ferrous base at the point of contact.

6. The method as set forth in claim 1 in which alloying is completed during vulcanization.

7. A rubber coated article comprising a ferrous metal base, a zinc coating over said base, a thin copper coating thereon having a thickness less than approximately 1/ 60,000 inch and of athickmess to alloy throughout with thezinc at atmospheric temperature or at the temperature 'of vulcanization, and produce a thin layer of brass thereon, and a coating of rubber vulcanized thereon.

8. An article as in claim 7 in which the zinc has a thickness of the order of .1 /4000 to 1/ 11,000 inch.

9. An article as in claim 7, in which the copper has a minimum thickness of the order of 1/240,000 inch.

10. An article as set forth in claim '7, in which the zinc has a thickness of the order of 1/4,000 to l/11,000 of an inch, and the copper has a rginimum thickness of the order of 1/240,000 inc 11. An article as set forth in claim 7 in which the zinc has a thickness of the order of 1/4000 to 1/11,000 of an inch, and the copper has a thickness of the order of 1/100,000 of an inch.

12. A ferrous base article, having a layer of zinc thereon, the thickness of zinc being of the order of 1/4000 to 1/11,000 inch, and a thin copper layer on the zinc, said layer of copper having a thickness less than approximately 1/60,000 of an inch and of a thickness to alloy throughout with the zinc at atmospheric temperature or at the temperature of vulcanization and produce a thin layer of brass thereon, said article being adapted for adherent vulcanization to rubber.

13. A ferrous base article adapted for adherent vulcanization to rubber, comprising a ferrous base, a layer of zinc thereon, the total thickness of zinc on the base being of the order of l/4,000 to 1/11,000 inch, and a copper layer adapted to alloy with the outer surface of the zinc, and of a thickness of the order of 1/60,000 to 1 /240,000 of an inch, whereby the copper and zinc form a thin layer of rubber adherent brass at atmospheric temperature or the temperature of vulcanization.

14. An article as set forth in claim 12 in which the copper has a weightof the order of .1 to .4' gram per square foot of surface.

15. A ferrous metal tire bead wire having high elasticityand elongation limits and of a thickness of the order of .037 to .043 inch and adapted to be adherently vulcanized to a tire bead, having a wiped galvanized layer of zinc thereon, and a layer of copper thereon having-a weight of the order of .1 to .4 gram per square foot of surface, whereby the copper and zinc form a thin layer of rubber adherent-brass at atmospheric temperature or the temperature of vulcanization,

whereby during vulcanization of the wire to the tire bead the rubber adheres to the formed brass layer.

16. A ferrous base article adapted for adherent vulcanization to rubber and consisting of a ferrous base portion, a zinc iron alloy layer merging into a surface of the ferrous base portion, a zinc layer merging into the zine-iron alloy layer, the zinc and alloy layer together being of the order of 1/4,000 to l/ 11,000 inch thick, an outer thin layer of copper not over approximately 1/60,000 inch thick and thick enough to form a rubber adherent layer of brass at atmospheric temperature or the temperature of vulcanization, whereby during vulcanization to the article of a rubber layer the latter is bonded to the zinc by the brass layer.

17. The product of claim l6 in which the article is a tire bead wire, and the several metallic layers surround all the wiresurface.

18. In the production of galvanized steel wire,

the step of dipping a flexible steel tire bead reinforcing wire having a diameter of the order of .037-.043 inch and having a carbon content of the order of 0.65% and a manganese content of the order of 30%, in molten zinc at a temperature of the order of 849 F. for a period of the order of one to five seconds, whereby the base is coated with zinc, and the elongation limit thereof is substantially increased.

ELGIN CARLTON DOMM. 

